I changed my Add-in settings in the Trust Center settings to match yours (Require Application Add-ins to be signed: ON, Disable notification for unsigned add-ins: ON, Disable all Application Add-ins: OFF) and the Esri Maps toolbar works just fine for me. I'm able to sign in, insert a map, etc. I don't think this is your issue.
I do believe the issue is with your ArcGIS Connection in the Esri Maps backstage. Are you trying to connect to a Portal for ArcGIS server or are you trying to connect to ArcGIS Online?